The present invention relates, in general, to semiconductor structures, and more particularly, to semiconductor structures utilizing titanium nitride as a dopant diffusion barrier.
Previously, the semiconductor industry has employed wafer bonding techniques to attach an active semiconductor wafer to a handle wafer. The handle wafer generally is used to support the active wafer during subsequent processing and assembly operations. A problem arises when the active wafer has doped semiconductor regions that are electrically connected by metal areas. At the high temperatures utilized to perform wafer bonding, previous conductor materials, such as tungsten-silicide, provide a migration path that allows dopants to diffuse from one doped semiconductor area to another. This diffusion path permits P-type dopants to counter dope N-type areas, and N-type dopants to counter dope P-type areas thereby degrading or destroying the semiconductor device's operation. The diffusion occurs both laterally and transversely through the conductor. The lateral diffusion occurs near the surface that forms an interface between the conductor and the doped regions. Such lateral diffusion through the conductor near the metal-semiconductor interface destroys ohmic contact between the conductor and the doped areas by counter doping a portion of the doped area that is in contact with the conductor. The transverse diffusion is perpendicular to the conductor's surfaces and can degrade a semiconductor device's performance by transporting dopants from desired positions.
Accordingly, it is desirable to have a conductor that functions as a dopant diffusion barrier at high temperatures, that maintains ohmic contact during high temperature operations, and that facilitates bonding a handle wafer to an active semiconductor wafer.